Battery pack

ABSTRACT

A battery pack features a shock-absorbing and sealed construction and an electronic control module that provides automatic recovery circuitry in the event of a short circuit in the load whereby the power is terminated and then restarted at a lower level so that removal of the short circuit may be detected. Full power is restored to the load when the short circuit is removed. In addition, the electronic control module of the battery pack uses the battery pack load, such as a cap lamp, to provide an indication of a low battery charge level. The electronic control module also provides a soft-start feature where the power provided to the bulb is ramped up to avoid current in-rush to the bulb during startup.

CLAIM OF PRIORITY

This application claims priority from U.S. Provisional PatentApplication Ser. No. 60/880,330, filed Jan. 12, 2007.

FIELD OF THE INVENTION

The invention relates generally to battery packs and, more particularly,to a battery pack that features a durable construction and operationdirected by an electronic control module.

BACKGROUND OF THE INVENTION

Rechargeable battery packs find use in many industrial applications dueto their portability, dependability and low maintenance cost. A commonusage of rechargeable battery packs is to power lamps mounted on hardhats worm by miners. Such cap lamps provide illumination in undergroundmine shafts. Cap lamps are well known in the mining equipment industryand provide illumination while the miner's hands remain free to performtasks.

The battery pack is typically secured to the user's waist and electricalwiring delivers power from the battery pack to the lamp on the helmet.Normally, at the end of each working shift, the helmet and battery packare removed by the miner and the battery pack is placed in a rechargingdevice so that it is ready for use during a future shift. An example ofsuch a cap lamp and rechargeable battery pack arrangement is disclosedin U.S. Pat. No. 4,481,458 to Lane.

Lithium-ion (Li-ion) batteries have a higher energy-to-weight ratio thenany other commercially available rechargeable batteries. This makes themvery desirable as a power source for portable devices, such as caplamps. Most Li-ion battery packs, including those used to power miningcap lamps, must have a safety protection circuit to protect them fromover-voltage, under-voltage and over-discharge conditions.

In addition, Li-ion battery packs often feature an electronic controlmodule in series between the batteries and the cap lamp (or other load)to control operation of the battery pack. Such electronic controlmodules may include circuitry or a microprocessor that functions toprovide an indication of a low battery, control battery charging andother functions. A need exists, however, for a low battery indicatorthat is easier to detect and that provides extended cap lamp operationso that a mine may be exited.

Electronic control modules may also cause a Li-ion battery pack to gointo protection mode in the event of a short circuit. Such shortcircuits may be caused by, for example, worn parts in the cap lampassembly or wires leading thereto. When the battery pack goes intoprotection mode, the cap lamp (or other load) is automatically turnedoff. Prior art designs require the user to manually turn the lamp offand then back on to reset the electronic control module or othercircuitry and allow current to resume flow to the cap lamp after theshort circuit condition is removed. An electronic control module thatautomatically turns the lamp (or other load) back on when the shortcircuit condition is removed is desirable.

A mine provides a very harsh atmosphere for equipment, including batterypacks. The mine atmosphere contains an abundance of dirt, dust, coalparticles and moisture. In addition, there is always the potential of abuild-up of explosive gases in a mine. As a result, it is important toeffectively seal a battery pack so that harmful elements can't reach thebattery or the related wiring and circuitry inside. Furthermore, batterypacks used in mines may suffer mechanical abuses during use as they arebanged against machinery and rock, dropped and/or jostled as they rideon the user's waist. As a result, a need exists for a battery pack thatcan withstand shocks and vibrations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded top front perspective view of a battery packincluding an embodiment of the electronic control module of the presentinvention;

FIG. 2 is a perspective view of the battery cell bundle without a wrapor pads with an electronic control module and protection circuitassembled thereto;

FIG. 3 is a bottom plan view of the battery cell bundle of FIG. 2;

FIG. 4 is a perspective view of the battery pack of FIG. 1 after beingassembled;

FIG. 5 is a block diagram illustrating the primary components of theelectronic control module of the battery pack of FIGS. 1-4;

FIG. 6 is an operation flow diagram of the microprocessor of theelectronic control module of FIG. 5.

FIG. 7 is a schematic of the charging section circuit of the electroniccontrol module of FIG. 5;

FIG. 8 is a schematic of the low battery warning/indication circuit ofthe electronic control module of FIG. 5;

FIG. 9 is a schematic of the microprocessor and associated circuitry ofthe electronic control module of FIG. 5;

FIG. 10 is a schematic of the battery sensing circuit of the electroniccontrol module of FIG. 5;

FIG. 11 is a schematic of the overload sensor circuit of the electroniccontrol module of FIG. 5;

FIG. 12 is a schematic of charge current sensor circuit of theelectronic control module of FIG. 5;

FIG. 13 is a schematic of the LED driver circuit of the electroniccontrol module of FIG. 5.

DETAILED DESCRIPTION OF EMBODIMENTS

While the battery pack of the invention is described below in terms ofuse in powering a cap lamp of the type used in the mining industry, itmay find application in other industries with other battery-powereddevices. Indeed, the electronic control module of the invention may beintegrated into a battery-powered device itself or a load attached tothe battery pack, instead of a separate battery pack. In addition, whilethe battery pack described below features Lithium-ion (Li-ion) batterycells, the battery pack of the invention may feature other types ofbattery cells.

An embodiment of the battery pack of the present invention isillustrated in an exploded view in FIG. 1. The battery pack includes abattery housing or jar 7, that is preferably made of polycarbonate, withan open top end. A cover 8, also preferably made of polycarbonate,removably covers the open top of the battery jar, as illustrated in FIG.4.

As illustrated in FIG. 1, a battery cell bundle 9 is positioned withinthe battery jar 7. The bundle features battery cells, indicated at 10 inFIGS. 2 and 3, wrapped with a foam vibration-reducing wrap 11. The foamwrap is preferably composed of neoprene and ethylene propylene dienemonomer (EPDM) and is preferably approximately 2″×7.5″× 1/16″ thick. Inaddition, a pair of pads, one of which is indicated in phantom at 12 inFIG. 1, are positioned on opposite sides of the bundle, between thecells and wrap. Each pad 12 is preferably constructed from the samematerial as the wrap and is preferably approximately 1.25″×2.5″× 1/16″thick.

Enlarged views of the battery cell bundle 9 of FIG. 1 with the wrap andpads (11 and 12 in FIG. 1) removed are provided in FIGS. 2 and 3. Whileeight battery cells 10 are illustrated, the battery pack could includean alternative number of cells. In addition, the cells preferably areLi-ion battery cells. As an example only, the battery pack may have amaximum voltage of 4.2 Volts DC and a minimum voltage of 2.5 Volts (V)DC. The battery pack may discharge at up to 2 amp, and may charge at upto 2.5 amp (A), also as an example only. The terminals of the batterycells 10 engage contact plates 13 a (FIG. 1) and 13 b (FIG. 3) which, aswill be explained in greater detail below, are joined to a protectioncircuit, illustrated at 15 in FIGS. 2 and 3.

As illustrated in FIG. 1, a separator plate 17 (preferably also made ofpolycarbonate) is positioned over the battery cell bundle 9 so that abattery compartment is formed below and is secured within the batteryjar 7 by adhesive, preferably so that the edges seal against theinterior walls of the battery jar 7. As a result, an electronic controlmodule compartment is defined within the jar or housing 7 above theseparator plate. An electronic control module (ECM) 20, which containscircuitry and a microprocessor, as described in greater detail below, ispositioned on top of the separator plate 17, and communicates with theprotection circuit 15 of FIGS. 2 and 3, and thus the battery cell bundle9, via a pair of wires 19 (FIG. 2) that travel through notches 21(FIG. 1) of separator plate 17. The circuitry and microprocessor of theECM is preferably potted in a potting compound for protection. Pottingcompounds for circuitry and the like are well known in the art.

The protection circuit 15 of FIGS. 2 and 3 is in circuit with the wiresleading from the battery pack to the ECM and provides under-voltagecutoff, over-voltage cutoff and over-current cutoff protection. Theprotection circuit may be a standard, off-the-shelf circuit, such as theVC3053 from Venture Inc. As illustrated in FIGS. 2 and 3, the protectioncircuit 15 preferably is housed in a box-like structure composed ofthermally conductive potting compound. This protects the printed circuitboard and components from stress and vibration.

As illustrated in FIGS. 1 and 2, the ECM 20 includes positive andnegative posts 14 a and 14 b and a charging status light emitting diode(LED) 16. As illustrated in FIG. 1, a pair of O-ring seals 18 arepositioned over the positive and negative posts of the ECM 20 so thatthey are sandwiched, and thus form a seal, between the top surface ofthe ECM 20 and the bottom surface of the battery post holder 22.

The battery jar 7 and battery post holder 22 are preferably sonicallywelded together to seal the battery cell bundle, ECM, and other internalcomponents inside the battery jar where they are protected from dirt andmoisture. The cover 8 is reversible and secured to the battery jar 7with cover hold down screws 24 (FIG. 1) and a gasket, which may bemolded into the cover 8, for easy service and removal as well aseffective sealing. The back side of the battery jar may be provided witha clip (not shown) so that the battery pack may be mounted on the beltof a user and may also feature a plug 26 (FIG. 1) that seals acorresponding hole formed in the battery jar 7 so as to serve as apressure relief valve.

The cover 8 includes a cord strain relief 28 (FIGS. 1 and 4), preferablyconstructed of a rubber material, that receives insulated wires thatattach to positive and negative posts 14 a and 14 b to provide power tothe cap lamp. An example of such a cap lamp is provided in U.S. Pat. No.4,481,458 to Lane, the contents of which are hereby incorporated byreference. The cover also features elongated, transparent windows 32 aand 32 b (FIG. 4) which are illuminated by the LED 16 (FIGS. 1 and 2).

The operational features of the ECM 20 preferably include the chargingstatus LED (16 in FIGS. 1 and 2), short circuit protection, a lowbattery warning, a soft-start feature and a 2:1 charging/dischargingratio. In addition, the ECM preferably includes a charging voltage andcurrent converter so that the battery pack may be used with chargersoriginally designed for lead-acid type batteries.

A block diagram illustrating the primary components and circuitry of theECM 20 of FIGS. 1 and 2 is provided in FIG. 5. As illustrated in FIG. 5,the ECM includes a microprocessor 34. The ECM also includes a chargingsection circuit 36, a low battery warning circuit 38, an LED drivercircuit 40, a battery sensing circuit 42, a charge current sensorcircuit 44 and an overload sensor circuit 46, all of which communicatewith the microprocessor 34.

A flow chart illustrating the programming of the microprocessor 34 ofFIG. 5 is provided in FIG. 6. As indicated by block 47 of FIG. 6, whenmicroprocessor 34 is initially powered up, that is, connected to power,a number of default settings for the ECM occur. More specifically,transistors Q4 and Q5 of the charging section circuit, illustrated inFIG. 7, are turned off. As will be explained in greater detail below,transistors Q4 and Q5 of the charging section circuit are responsiblefor controlling current flow to and from the battery pack duringcharging and discharging.

In addition, the charging status LED 16 (FIGS. 1, 2 and 13) is turnedoff as a default setting of the ECM. The charging status LED 16 iscontrolled by the microprocessor via the LED driver circuit 40 (FIGS. 5and 13) and illuminates windows 32 a and 32 b of the battery pack (FIG.4) with either a red or green color to indicate charging status. Morespecifically, a red LED is an indication that the battery is connectedto a charger and is accepting a charge current. A green LED is anindication that the battery is connected to a charger, but it is nolonger accepting charge current because it is fully charged and readyfor operation. The operation of the LED driver circuit will be explainedin greater detail below.

A “LAMP_WAS_ON” bit that is internal to the microprocessor is also setto “1” as the default setting of the ECM. This bit is an indication ofwhether the fully charged battery pack was used after being charged.This prevents the battery pack from being charged if it is disconnectedand reconnected to a charger without application of a load. Charging ofthe battery pack may occur only if the bit is set to “1.”

Next, as illustrated at 48 in FIG. 6, the LED_GREEN pin of themicroprocessor is checked for a high or low setting. The LED_GREEN pinis illustrated at 49 in FIG. 9 as is microprocessor 34. The high settingof the LED_GREEN pin corresponds to the charging status LED 16 beingilluminated in green, and thus corresponds to the battery pack being ina fully charged condition. If this is the case, the battery pack goesinto monitoring mode, as illustrated at block 50 in FIG. 6, where thebattery capacity is monitored. If the battery voltage falls below athreshold due to self-discharge, and the battery pack is connected to acharger, charging restarts, as will be explained below.

When the LED_GREEN pin 49 (FIG. 9) of the microprocessor is set to high,this is communicated to the to the LED driver circuit 40 (FIGS. 5 and13) via connection 43 of FIG. 13 so that, as noted above, the chargingstatus LED is illuminated in green. Power is received by this portion ofthe LED driver circuit 40 by connection 45 (FIG. 13).

If the LED_GREEN pin of the microprocessor is low, the charging statusLED is not illuminated in green. If this is the case, as indicated at 51in FIG. 6, the microprocessor checks the battery pack for anover-discharged condition. More specifically, the battery sensingcircuit 42 of FIG. 5 is illustrated in greater detail in FIG. 10 andfeatures a voltage divider or measurement portion, indicated in generalat 53. The voltage measurement portion 53 of FIG. 10 communicates viaconnection 55 with line 56 of the charging section circuit of FIG. 6,and thus the positive and negative terminals of the battery cell bundle,illustrated at 15 a and 15 b, respectively, in FIG. 8, and determinesthe battery cell voltage. The battery cell voltage is communicated bythe battery sensing circuit of FIG. 10 to the microprocessor via theconnection 57 (BAT) of FIG. 10 and corresponding input pin 59 (FIG. 9)of the microprocessor. If the battery cell voltage is equal to or lessthan 2.5V, the battery pack is in an over-discharged condition and, asindicated at 61 in FIG. 6, the charging status LED and transistors Q4,Q5 and Q8 (FIG. 6) are shut off. As will be explained in greater detailbelow, pulse transistor Q8 is responsible for controlling current duringpulse width modulation operation of the battery pack. If the batterycell voltage is greater than 2.5V, the next step of FIG. 6 is performedby the microprocessor.

As indicated at 63 in FIG. 6, the microprocessor next checks for a faultcondition, such as a short circuit or overload condition. As describedpreviously, the ECM must handle a short circuit or overload (the term“short circuit” being used to mean either situation herein), such ascaused by worn parts in the load or wires leading thereto, by causingthe battery pack to go into protection mode so that the load (a cap lampin the present example) is turned off. Prior art designs require theuser to manually turn the cap lamp off and back on to reset theassociated circuit prior to allowing current flow back to the cap lampafter the short circuit condition is removed. The ECM of the presentinvention features circuitry that automatically turns the cap lamp (orother load) back on after the short circuit condition is removed. Inother words, the user does not have to manually turn the cap lamp offand back on to reset the battery pack.

With reference to FIG. 5, the automatic recovery feature is provided bythe microprocessor 34, charging section circuit 36 and low batterywarning circuit 38 of the ECM. As noted previously, schematicsillustrating the details of an embodiment of the charging section andlow battery warning circuits are provided in FIGS. 7 and 8,respectively, while a schematic illustrating the microprocessor 34 andassociated circuit is provided in FIG. 9.

With reference to FIG. 7 and as noted previously, the positive andnegative terminals or posts of the battery pack are illustrated at 14 aand 14 b, respectively. During the discharge of the battery (such aswhen it is powering a load/cap lamp) current from the load and post 14 bflows through ground point 52 (FIG. 7) to ground point 54 (FIG. 8),through resistor R25 and negative terminal 15 b of the battery cellbundle (9 in FIG. 1) into the battery cell bundle. Current from thebattery cell bundle flows through battery cell bundle positive terminal15 a, line 56 (FIG. 8) and line 58 (FIG. 7). As illustrated in FIG. 7,the current traveling through line 58 encounters transistor Q5 and thentransistor Q4 before traveling to the positive post of the battery pack14 a and out to the cap lamp load.

In addition to the microprocessor pins already described, as illustratedin FIG. 9, microprocessor 34 features a number of input and output pinswhich are connected to the various circuits illustrated in FIG. 5. Theinput pins are illustrated on the left side of the microprocessor 34 inFIG. 9 while the output pins are illustrated on the right side. Thecharging section circuit 36 of FIG. 7 communicates with themicroprocessor voltage input pin Uinp 62 (FIG. 9) via connection 64(FIG. 7). In addition, with reference to FIG. 7, connections 66 and 68(CHARGE ON) and 72 (LOAD OFF) of charging section circuit 36 communicatewith corresponding output pins 74 and 76 of the microprocessor 34. Thelow battery warning/indication circuit 38 of FIG. 8 features connections78 (BATT ON) and 80 (DATA1) that communicate with corresponding pins 82and 84, respectively, of the microprocessor 34 of FIG. 9.

A coulomb counter, illustrated at 85 in FIG. 8, senses the dischargecurrent flowing through resistor R25. The sensed current is outputtedfrom the coulomb counter 85 through connection 86 (Is). The sensedcurrent is monitored via overload sensor circuit 46 (FIGS. 5 and 11) asthe circuit receives the sensed current through connections 86 (FIG. 8)and 88 (FIG. 11). As illustrated in FIG. 11, an operational amplifier 92receives the sensed current from 88 and is programmed to check for theshort circuit condition (indicated by a high current flow). When such acondition is detected, a signal indicating a short circuit condition isprovided to the microprocessor via connection 94 (FIG. 11) andmicroprocessor input pin 96 (FIG. 9) so that the microprocessor inputpin 96 (Overload Sens) is set to high. When conditions are normal (noshort circuit), the Overload Sens input pin 96 of the microprocessor isset to low.

When a short circuit is sensed, as indicated at 63 and 97 in FIG. 6, themicroprocessor turns off transistor Q5, and thus the load (cap lamp),via pin 76 (FIG. 9) and, with reference to FIG. 7, connection 72 andswitch Q2 so that current may flow through line 99 and thus pulsetransistor Q8. In addition, transistors Q4 and Q8 are turned off by themicroprocessor via output pin 74 (FIG. 9) and, with reference to FIG.7), connections 66 and 68 and switches Q1 and Q10.

Next, as illustrated at 100 in FIG. 6, the voltage level at theterminals of the battery pack (Uinp) is measured using connection 64 ofFIG. 7 and corresponding input pin 62 (FIG. 9) of the microprocessor todetermine if the short condition still exists. If so, as indicated byblock 101 in FIG. 6, pulse width modulation using pulse transistor Q8(FIG. 7) occurs until the load/cap lamp turns on. The pulsing oftransistor Q8 allows small amounts of current to flow, all being sensedby the comparator circuit, indicated in general at 102 in FIG. 7. If theshort circuit is still present, the comparator 102 will detect a rapidcurrent rise when transistor Q8 is turned on. The microprocessor will beso signaled by the comparator through the overload sensor circuit asconnection 104 (FIG. 7) of the comparator communicates with connection88 of the overload sensor circuit (FIG. 11). When the short circuit isstill present, the microprocessor will continue to pulse transistor Q8while sensing the current.

When the short circuit is removed, the microprocessor turns transistorQ5 on so that full current is restored to the cap lamp. As a result, thecircuitry provides a self-resetting mechanism so that when the batteryis shut down due to a short circuit, the load/cap lamp is automaticallyre-powered when the short circuit or is removed. No additional action isrequired by the user.

While the ECM of the present invention offers an automatic recoveryfeature for short circuits, a battery pack or load may optionally alsofeature a push-button or switch that resets the system and re-powers theload after the battery is shut down due to a short circuit when theshort circuit is removed.

The charging section circuit 36 of FIGS. 5 and 7 of the ECM alsopreferably provides the battery pack with a “soft-start” feature toavoid a massive inrush of current into the cap lamp bulb at start up,and thus increase bulb life. When the cap lamp is shut off, themicroprocessor shuts off transistors Q4 and Q5 so that when the cap lampis switched on or connected to the battery pack terminals, current mustflow through branch 99 of FIG. 7. The ramp-up of electrical current(soft-start) is accomplished by pulse width modulation via transistor Q8as controlled by the microprocessor 34. More specifically, transistor Q8is controlled in this manner as current flows to the cap lamp until fullcurrent is achieved and communicated to the microprocessor. Once fullcurrent is achieved, transistors Q4 and Q5 are turned on by themicroprocessor and transistor Q8 is turned off. Full current then flowsto the cap lamp as described above.

Returning to FIG. 6, if no short circuit condition exists, themicroprocessor checks for the presence of a charging current, asindicated at 106. More specifically, a charge current circuit sensorcircuit 44 (FIGS. 5 and 12) receives the current sensed in the circuitof FIGS. 7 and 8 via connections 86 (FIG. 8) and 108 (FIG. 12). If acharge current is sensed, with the assistance of operational amplifier110 of FIG. 12, input pin 112 (ICharge) of the microprocessor (FIG. 9)is notified via connection 114 (FIG. 12) so that ICharge>0 for purposesof 106 in FIG. 6. The flow chart then branches to the charge mode, asillustrated by FIG. 6.

For recharging, the battery pack is placed in a charging rack having aconnector that engages a corresponding charging connection on the caplamp. Such charging racks are well-known in the art. During recharging,the charging current enters the battery pack through the positive post14 a (FIG. 7) of the battery pack and travels the reverse of the batterypack discharge route described above so that the charging current passesthrough transistor Q4 and then transistor Q5. The charging current exitsthe battery pack through negative post 14 b. The charge ratio for thebattery pack preferably is 2:1. Therefore, for every twelve hours ofuse, it will take six hours to recharge the battery pack.

As illustrated at 116 in FIG. 6, the LAMP_WAS_ON internal bit of themicroprocessor 34 is again checked to ensure that it is set to 1, sothat charging is permitted. If the LAMP_WAS_ON bit is set to 0, the ECMis set to default for discharge mode whereby the charging status LED isilluminated in green, Q4 is turned off and Q5 is turned on, as indicatedat 118 and 120 in FIG. 6. In addition, as indicated at 120, the coulombcounter count is set to 16 amp hours (Ah) as an indication of fullcharge for the battery pack via output pin 84 (FIG. 9) of themicroprocessor and connection 80 of FIG. 8. Flow then branches back tostep 51, as illustrated in FIG. 6, so that the top portion of the flowchart, including the short circuit check section, is performed.

If LAMP_WAS_ON=1, the battery pack has been discharged an unknown amountand must go into active charge mode and the next step, 122 of FIG. 6, isperformed. At 122, the battery cell voltage is checked by themicroprocessor (via measurement portion 53 of the circuit of FIG. 10,connection 57 of FIG. 10 and microprocessor input pin 59 of FIG. 9). Ifthe battery cell voltage is less than or equal to 4.2V, the flowchartbranches to current mode, as illustrated in FIG. 6. In current mode, asindicated at 124, a timer (125 in FIG. 9) is started and the chargingstatus LED (16 in FIGS. 1, 2 and 13) is illuminated in red. With regardto the latter, the microprocessor sends a signal to the LED drivercircuit 40 (FIGS. 5 and 13) via microprocessor output pin 126 (FIG. 9)and connection 128 of FIG. 13. Power is received by this portion of theLED driver circuit by connection 130. In addition, during current mode,pulse width modulation via resistor Q8 is activated.

As indicated at 132 in FIG. 6, the charging current Ibat (or Icharge) ismonitored by the microprocessor. This occurs via the charge currentsensor circuit 44 of FIGS. 5 and 12 and input pin 112 of themicroprocessor (FIG. 9). The microprocessor adjusts the charging currentby increasing or decreasing the pulse width modulation duty cycle oftransistor Q8 (FIG. 7), as indicated by 134 a and 134 b in FIG. 6. As aresult, a 2.5 A mean charge current is achieved while the batterycharging state is at a constant current. Flow then branches back to step51, as illustrated in FIG. 6, so that the top portion of the flow chart,including the short circuit check section, is performed. The currentmode of charging occurs until the battery cell voltage is greater than4.2V, at which time voltage mode is initiated.

As illustrated at 136 in FIG. 6, the pulse width modulation oftransistor Q8 continues and the charging status LED is illuminated inred during the voltage mode of charging. As indicated at 138, the timer125 (FIG. 9), which was turned on at 124 of FIG. 6, is checked todetermine if it is greater than the timeout value (Tmax). If so, asillustrated in FIG. 6, the charging status LED is illuminated in green,charging is stopped and the discharge mode is initialized as indicatedat 118 and 120 in FIG. 6. The timer is used for safety purposes andvoltage mode rarely terminates due to the timer exceeding the timeoutvalue.

If the timeout value has not been exceeded at 138 in FIG. 6, thecharging current is checked at 142 by the microprocessor to determine ifit is greater than the value Imax10%. Imax10% is equal to 10% of themaximum constant current (Imax) in the current mode. This is the typicaltermination mechanism for charging. If the charging current is notgreater than Imax10%, the charging status LED is illuminated in green,charging is stopped and the discharge mode is initialized as indicatedat 118 and 120 in FIG. 6.

Returning to 106 in FIG. 6, if no charging current is present, themicroprocessor, and thus the ECM, enters the discharge mode, asindicated at 144. As indicated by 146 in FIG. 6, capacitors Q4 and Q5(FIG. 7) are turned on and the charging status LED is illuminated ingreen. Next, as indicated at 148, the coulomb counter (85 in FIG. 8)count is checked by the microprocessor as an indication of the chargelevel of the battery pack. If the count is greater than or equal to 2Ah, normal discharge mode continues and processing loops back to step 51as illustrated in FIG. 6. As a result, a short circuit and generalmonitoring mode is performed continuously, whether the battery pack isin charge or discharge mode.

If the coulomb counter count is less than 2 Ah, the battery pack goesinto low power mode where a low battery charge warning is provided. Morespecifically, as indicated at 152 in FIG. 6, the microprocessor turnstransistors Q4 and Q5 (FIG. 7) off and operates Q8 in pulse widthmodulation mode so that the discharge of the battery pack occurs at lowpower. This causes the cap lamp load to dim. The dimmed light providesextended time for a miner to depart from the mine and obtain a fullycharged battery pack. In addition, as indicated at 154 and 156 in FIG.6, every two minutes the microprocessor turns on transistors Q4 and Q5for one second so that the cap lamp flashes with full power, which actsas a warning of a low battery charge condition. As indicated at 158,operation of Q8 in pulse width modulation mode resumes after the flashso that the cap lamp is again dim.

The microprocessor 34 of FIGS. 5 and 9 requires a constant voltage torun. This is provided by the voltage regulator 162 of the circuit ofFIG. 10. More specifically, as noted previously, the circuit of FIG. 10receives voltage from the battery cell bundle (VDD) via connection 55.This is converted by the voltage regulator 162 to voltage (VCC) that isprovided to the microprocessor, and other components of the ECM such asthe coulomb counter 85 of FIG. 8 and the operational amplifiers 92 and110 of FIGS. 11 and 12, respectively, via connection 164 (FIG. 10).

As noted previously, the battery pack is provided with a protectioncircuit illustrated at 15 in FIGS. 2 and 3 that provides under-voltagecutoff, over-voltage cutoff and over-current cutoff protection. Theprotection circuit therefore acts as a backup to the ECM circuitry andmicroprocessor programming discussed with respect to FIG. 6. As examplesonly, an over-voltage condition may occur if the protection circuitdetects a voltage of 4.35V or greater, while an under-voltage conditionmay occur if the protection circuit detects a voltage of 2.5V or less.An over-current condition may exist if the current exceeds 4.5 A. If anyof these conditions exist, the protection circuit is tripped like acircuit breaker. As a result, the protection circuit must be resetbefore the battery pack may be used again.

The protection circuit is reset using the capacitor bank circuitindicated in general at 172 in FIG. 8. Transistor QB6 (FIG. 8) permitsenergy to flow into the capacitor bank circuit 172, but does not permitit to escape until so directed by the microprocessor. As a result,energy is stored in the capacitor bank circuit 172. When the protectioncircuit (15 of FIGS. 2 and 3) is tripped, input pin 59 (FIG. 9) of themicroprocessor goes to zero and the microprocessor signals the capacitorbank circuit 172 to release the stored energy via connection 78 (FIG. 8)and microprocessor output pin 82 (FIG. 9). This release of energy causesthe battery protection circuit to reset.

The voltages, currents and times of FIG. 6 are presented as examplesonly and are in no way to limit the scope of the invention.

While the preferred embodiments of the invention have been shown anddescribed, it will be apparent to those skilled in the art that changesand modifications may be made therein without departing from the spiritof the invention, the scope of which is defined by the appended claims.

1. A battery pack comprising: a. a housing; b. a battery cell positionedwithin said housing; c. a pair of terminals attached to said housing forproviding power from said battery cell to a load; d. an electroniccontrol module positioned within said housing and in series between saidpair of terminals and said battery cell; and e. said electronic controlmodule detecting when a fault condition exists in the load and, afterterminating current flow from the battery cell to the terminals,providing a reduced current flow to the load while sensing the reducedcurrent flow and restoring full current flow when sensing that the faultcondition no longer exists in the load.
 2. The battery pack of claim 1wherein said electronic control module includes a transistor and amicroprocessor and said microprocessor provides a reduced current flowto the load when the fault condition is present by pulsing thetransistor.
 3. The battery pack of claim 2 wherein the transistor iscontrolled by the microprocessor to subject the current to pulse widthmodulation.
 4. The battery pack of claim 1 wherein the fault conditionis a short circuit.
 5. The battery pack of claim 1 wherein the load is acap lamp.
 6. The battery pack of claim 1 wherein said electronic controlmodule includes a microprocessor.
 7. The battery pack of claim 6 whereinthe electronic control module includes an overload sensor circuit havingan input that receives a sensed current flowing from the battery pack tothe load and an output in communication with the microprocessor, saidoverload sensor circuit sending an indication to the microprocessor whenthe fault condition exists based on the sensed flow of current.
 8. Thebattery pack of claim 7 wherein the overload sensor circuit includes anoperational amplifier having an input receiving a sensed flow of currentfrom the battery pack to the load and an output in communication withthe microprocessor.
 9. The battery pack of claim 1 wherein the batterycell is a Lithium-ion cell.
 10. The battery pack of claim 1 wherein theelectronic control module senses a current flowing from the battery packto the load to detect when a fault condition exists.
 11. A method ofautomatically restoring a flow of current to a load from a battery packafter a fault condition occurs in the load comprising the steps of: a.sensing a flow of current to the load; b. detecting when the faultcondition occurs in the load; and c. restoring a full flow of current tothe load when the fault condition is removed.
 12. The method of claim 11further comprising the steps of: a. terminating the flow of current tothe load after detecting when the fault condition occurs; b. providing areduced flow of current to the load after the flow is terminated; c.sensing the reduced flow of current to the load for removal of the faultcondition.
 13. The method of claim 12 wherein said reduced flow ofcurrent is provided by pulsing a transistor.
 14. The method of claim 13wherein the transistor is controlled by a microprocessor to subject thecurrent to pulse width modulation.
 15. The method of claim 11 whereinthe fault condition is a short circuit.
 16. The method of claim 11wherein the load is a cap lamp.
 17. A battery pack comprising: a. ahousing, b. a battery cell positioned within said housing; c. a pair ofterminals attached to said housing for providing power from said batterycell to a load; and d. an electronic control module positioned withinsaid housing and in series between said pair of terminals and saidbattery cell, said electronic control module monitoring battery usageand, after an amount of battery usage, limiting power to the load whileperiodically varying the power to the load so that the load acts asindicator of a low battery charge level.
 18. The battery pack of claim17 wherein said electronic control module includes a microprocessor thatmonitors battery usage and limits power to the load while periodicallyvarying the power to the load.
 19. The battery pack of claim 18 whereinsaid electronic control module includes a coulomb counter that is incommunication with the microprocessor and that the microprocessor usesto monitor battery usage.
 20. The battery pack of claim 17 wherein theelectronic control module limits power to the load by limiting currentflow to the load and periodically provides full current to the load tovary the power to the load so that the load acts as an indicator of alow battery.
 21. The battery pack of claim 20 wherein the electroniccontrol module includes a microprocessor and a transistor, saidmicroprocessor pulsing said transistor to limit current flow to theload.
 22. The battery pack of claim 21 wherein the transistor iscontrolled by the microprocessor to subject the current to pulse widthmodulation.
 23. The battery pack of claim 21 wherein the electroniccontrol module includes a timer in communication with themicroprocessor, said timer indicating to the microprocessor when toprovide full current to the load.
 24. The battery pack of claim 17wherein the load is a cap lamp.
 25. The battery pack of claim 17 whereinthe battery cell is a Lithium-ion cell.
 26. The battery pack of claim 17wherein the electronic control module provides a charge ratio of 2:1when the battery pack is connected to a charger.
 27. A method ofproviding an indication of a low battery charge level using a loadreceiving power from the battery comprising the steps of: a. monitoringbattery usage; b. limiting power to the load after a predeterminedamount of battery usage; and c. periodically varying the power to theload.
 28. The method of claim 27 wherein the step of limiting power tothe load is accomplished by limiting current flow to the load and thestep of periodically varying power to the load includes periodicallyproviding full current to the load.
 29. The method of claim 28 whereinthe step of limiting current flow to the load is accomplished by pulsinga transistor.
 30. The method of claim 29 wherein the transistor subjectsthe current to pulse width modulation.
 31. The method of claim 27wherein the load is a cap lamp.
 32. A battery pack comprising: a. ahousing; b. a battery cell positioned within said housing; c. a pair ofterminals attached to said housing for providing power from said batterycell to a load; and d. an electronic control module positioned withinsaid housing and in series between said pair of terminals and saidbattery cell, said electronic control module ramping up power to theload when the load is initially connected to the battery cell.
 33. Thebattery pack of claim 32 wherein the electronic control module includesa microprocessor, said microprocessor ramping up power to the load whenthe load is initially connected to the battery cell.
 34. The batterypack of claim 33 wherein the microprocessor ramps up power to the loadby ramping up a flow of current from the battery cell to the load. 35.The battery pack of claim 34 wherein the electronic control moduleincludes a transistor in communication with the microprocessor, saidmicroprocessor pulsing said transistor to ramp up the flow of currentfrom the battery cell to the load.
 36. The battery pack of claim 35wherein the transistor is controlled by the microprocessor to subjectthe current to pulse width modulation.
 37. The battery pack of claim 32wherein the load is a cap lamp.
 38. The battery pack of claim 32 whereinthe battery cell is a Lithium-ion battery cell.
 39. A method ofproviding a soft start for a load receiving power from a battery cellcomprising the steps of: a. connecting the load to the battery cell; andb. ramping up power supplied to the load from the battery cell until apredetermined power level for operating the load is reached.
 40. Themethod of claim 39 wherein step b. includes ramping up a flow of currentfrom the battery cell to the load.
 41. The method of claim 40 whereinstep b. is accomplished by pulsing a transistor.
 42. The method of step41 wherein the transistor subjects the current to pulse widthmodulation.
 43. The method of claim 39 wherein the load is a cap lamp.44. The method of claim 39 wherein the battery cell is a Lithium-ionbattery cell.
 45. A battery pack comprising: a. a housing having an openend; b. a separator plate positioned within said housing so that anelectronic control module compartment is defined adjacent said open endand a battery compartment is defined on an opposite side of theseparator plate; c. a battery cell positioned in the batterycompartment; d. an electronic control module positioned in theelectronic control module compartment, said electronic control module incommunication with the battery cell; e. a pair of battery pack terminalsin communication with the electronic control module; f. a battery postholder associated with the pair of terminals, said battery post holdersealing the otherwise open end of the battery housing; and g. a coverremovably attached to and sealing against the housing so that the pairof battery pack terminals are covered.
 46. The battery pack of claim 45wherein the electronic control module includes circuitry embedded in apotting compound.
 47. The battery pack of claim 46 wherein theelectronic control module includes a microprocessor embedded in apotting compound.
 48. The battery pack of claim 45 wherein the batterycell is part of a battery cell bundle.
 49. The battery pack of claim 48wherein the battery cell bundle is wrapped in a vibration-reducing wrap.50. The battery pack of claim 49 wherein the wrap is constructed fromneoprene and ethylene propylene diene monomer.
 51. The battery pack ofclaim 45 further comprising a protection circuit in series between thebattery cell and the electronic control module.
 52. The battery pack ofclaim 51 wherein the protection circuit is positioned in the batterycompartment.
 53. The battery pack of claim 52 wherein the protectioncircuit is embedded in a potting compound.
 54. The battery pack of claim45 wherein the cover includes a strain relief adapted to receive a powercord of a load.
 55. The battery pack of claim 45 wherein the cover isremovably attached to the housing by screws.
 56. The battery pack ofclaim 45 further comprising an charging status LED mounted on thebattery post holder and in communication with the electronic controlmodule.
 57. The battery pack of claim 56 wherein the cover includes awindow that is illuminated by the charging status LED.
 58. The batterypack of claim 45 wherein the battery post holder is ultrasonicallywelded to the housing.
 59. The battery pack of claim 45 wherein thebattery pack terminals extend through openings formed in the batterypost holder and O-rings surround each terminal so that the terminals aresealed against the battery post holder.
 60. The battery pack of claim 45wherein the housing is constructed from polycarbonate.